Malaria is a major cause of child mortality in much of Africa. The mosquito parasite, Plasmodium falciparum, accounts for greater than 25% of childhood mortality outside the neonatal period. In parts of Africa, malaria has been ranked first by the World Bank in terms of disability-adjusted life-years lost. Drug and insecticide resistance, as well as insufficiently developed and financed health services, have hampered efforts over the past twenty years to improve the situation. As a result, the malaria burden has remained largely unchanged.
Mortality in young children due to mosquito-borne malaria poses a significant world health problem. Insecticide-treated nets and fabrics have been developed since the 1980s as a promising tool for the prevention of malaria in endemic countries. Potent and safe synthetic pyrethroids, such as, permethrin, deltamethrin, lambda-cyhalothrin, alphamethrin, and cyfluthrin, are presently used to treat bednets and curtains by simply dipping the fabric into a solution containing the insecticide and allowing the solution to dry on the fabric. Provided that the nets or fabrics are not washed more than once to twice, insecticidal activity is retained for up to twelve months.
Many studies documenting the efficacy of these nets or fabrics to reduce the number of outbreaks of malaria in endemic areas have been conducted in several countries. Recently, the World Health Organization (WHO), along with twenty other donor agencies, supported four large-scale trials in Africa to document the impact of treated bednets on child survival. The results indicated that the reduction in child mortality with the use of treated nets ranged from 16-33%. Treated nets, in combination with the use of insect repellents, have been suggested as a primary means of protection for high-risk travelers. Although little evidence is presently available to document the efficacy of treated nets or fabrics for travelers at high risk, the available evidence is so compelling that specific recommendations are often issued to all travelers exposed to situations that place them at risk for malaria.
Bednets treated with insecticides have been effective in the control of malaria in many countries. The treated bednets are an effective method of vector control in areas endemic for malaria and greatly enhance personal protection. Although there is some concern that the placement of the insecticide-treated fabric in close proximity to the skin, eyes, or mouth of the person being protected may be harmful, existing toxicology data on pyrethroids indicates that unlike other types of insecticides, these chemicals have been shown to be very safe.
The application of a residual insecticide to fabrics as a means of personal protection against vector-borne diseases has been attempted for some time. During World War II, the impregnation of bednets and combat fatigues by the Soviet, German, and U.S. armies was first tried. In the late 1970s pyrethroids were used for this purpose; their high insecticidal activity combined with low mammalian toxicity made them ideal for treating fabrics. A scientific panel convened in 1983 by WHO reviewed the first laboratory evidence and recommended the initiation of field trials to assess the potential of this technology for disease control.
Unfortunately, currently employed techniques for treating fabrics with insecticides are unable to maintain an effective level of active ingredient at the surface of the net or fabric to kill or repel mosquitoes, especially after repeated washings. In addition, currently available methods for applying insecticides to fabrics are expensive, which make their use impractical for underdeveloped countries. Furthermore, the available techniques utilize emulsions that vary greatly between manufacturers and do not provide consistent and effective results.
Therefore, what is needed is a wash durable insecticide treated net or fabric wherein the active ingredient is easily incorporated into the fabric and is prevented from being washed off, thereby maintaining the insecticide at the fabric surface to permit interaction with target arthropods for a prolonged period of time, even after repeated washings.